Method and apparatus for treating the surface of a TCO material in a semiconductor device

Abstract

The present disclosure provides a method for treating a surface portion of a TCO material in a semiconductor device that includes a structure configured to promote unidirectional current flow. To practice the method, the surface portion of the TCO is exposed to an electrolyte and a current is induced in the device. The current allows the TCO material to be reduced in a manner that improves adhesion of a metallic material to the exposed surface portion relative to adhesion of the metallic material to an unexposed surface portion.

Description

[Technical Field]

[0001] The present invention relates generally to the field of semiconductor device manufacturing, and more particularly to methods and apparatus for treating the surface of transparent conductive oxide (TCO) materials in semiconductor devices. [Background technology]

[0002] Semiconductor devices often have metal elements that can be used to create electrical contact between the device and other external components. Metal elements can also be used to interconnect various portions of the semiconductor device.

[0003] For example, solar cells have metal electrodes that allow light-generated charge carriers to be removed from the device as electrical current. These metal electrodes can consist of patterned metal structures, such as a grid of metal fingers interconnected by bus bars, or they can consist of a blanket metal layer. Patterned structures are typically used on one or more of the solar cell's surfaces that are exposed to sunlight.

[0004] Electrochemical metal plating is a viable option used to deposit metal materials on the surface of solar cells to form metal electrodes. For example, to fabricate bifacial heterojunction solar cells, metal electrodes must be formed on TCO layers located on both sides of the solar cell. These TCO layers are typically composed of indium tin oxide (ITO) deposited on the p-type and n-type hydrogenated amorphous silicon layers of the solar cell.

[0005] Silver, the dominant metal used in solar cell manufacturing, is one of the most expensive. Therefore, replacing silver with a cheaper metal could significantly reduce the manufacturing cost of solar cells. However, forming metal electrodes on ITO by electrochemical methods has proven challenging due to problems with metal adhesion to ITO. This problem is particularly pronounced for copper electrodes. Adhesion of copper electrodes by patterned plating onto ITO layers has proven poor, as copper plated directly onto ITO has been found to delaminate after plating or upon mask removal. This poor adhesion reduces the electrical performance of solar cells due to high series resistance. Structural problems can also arise if the copper electrodes delaminate from the ITO.

[0006] It would be beneficial to have a method for plating copper electrodes onto ITO that alleviates the adhesion problems discussed above. Summary of the Invention [Means for solving the problem]

[0007] According to a first aspect, the present invention provides a method for treating a surface portion of a TCO material in a semiconductor device comprising a structure configured to facilitate unidirectional current flow, the method comprising: exposing a surface portion of the TCO material to an electrolyte suitable for electrochemically reducing a portion of the TCO material when a current is induced through a region of the TCO material; inducing a current in the TCO material; Including, The induced current reduces the TCO material in a manner that improves adhesion of the metallic material to the exposed surface portions relative to adhesion of the metallic material to the unexposed surface portions.

[0008] In some embodiments, a structure configured to facilitate unidirectional current flow includes a light absorbing layer and at least one carrier selective layer. For example, the structure can include an absorbing layer disposed between an electron selective film and a hole selective film.

[0009] In another embodiment, the structure configured to facilitate unidirectional current flow includes a pn junction. Inducing current flow in the TCO material may comprise generating current in the semiconductor device, for example, by "biasing" the pn junction. The pn junction can be biased by exposing the pn junction to radiation or by applying a voltage across the pn junction.

[0010] In some embodiments, the method further includes electrically interconnecting the electrode element to the semiconductor device. Additionally, the wetted electrode can be disposed within the electrolyte such that an induced current can flow through an electrical circuit including the electrolyte, the semiconductor device, the TCO material, the electrode element, and the wetted electrode.

[0011] While the method is being performed, at least a portion of the device is outside the electrolyte.

[0012] In some embodiments, the TCO material is disposed as a continuous layer on an n-type or p-type region of a semiconductor device, and the induced current flows across this layer.

[0013] Advantageously, this provides better uniformity of the adhesion properties of the TCO across the layer.

[0014] The TCO material can be disposed as a continuous layer on an n-type region of a semiconductor device, and an electric current can be induced by exposing a portion of the semiconductor device to electromagnetic radiation.

[0015] In some embodiments, a voltage is applied between the semiconductor device and a wetted electrode in an electrolyte to reduce the voltage drop at the pn junction caused by electromagnetic radiation.

[0016] Advantageously, this applied voltage can be used to compensate for the radiation-induced self-bias of the pn junction and promote current flow.

[0017] By modulating properties such as the magnitude of the induced current, one can control one or more structural or electrical properties of the surface of the TCO layer. This can be done by modulating the intensity of the radiation or the applied voltage.

[0018] Alternatively, the TCO material can be disposed as a continuous layer on a p-type region of a semiconductor device, and current can be induced by applying a forward bias voltage across the junction using electrode elements.

[0019] By modulating a property such as the magnitude of the applied voltage, one or more structural or electrical properties of the surface of the TCO layer can be controlled.

[0020] In some embodiments, the method is performed in a manner such that the TCO material is etched during the method. The concentration of metal elements in the TCO material at the surface may also increase during the method. In some cases, the roughness of the exposed portion may also increase.

[0021] One or more properties of the electrolyte can be intentionally selected to affect the properties of the surface of the TCO material after treatment.

[0022] In some embodiments, prior to exposing the surface of the TCO material to the electrolyte, a mask is formed on the TCO material to define the patterned surface that will be exposed to the electrolyte.

[0023] In some embodiments, the electrolyte includes H2SO4. The weight concentration of H2SO4 in the electrolyte may be between 0.1% and 10%. The electrolyte may further include Na2SO4 at a weight concentration of 0.05% to 0.25%.

[0024] In some embodiments, the total amount of charge transferred to the TCO material throughout processing is less than 1 mC / cm 2 ~50mC / cm 2 and in certain embodiments, 15 mC / cm 2 ~25mC / cm 2 is included between.

[0025] In some embodiments, the method can include plating a metal onto the surface of the TCO material. The plating can be performed by electric field induced plating, light induced plating, or electroplating.

[0026] After carrying out the method according to the first aspect, adhesion of the plated metal to the TCO is improved.

[0027] In some embodiments, the adhesion of the metal to the TCO material is greater than 0.5 N per mm of busbar width as measured by a busbar tensile tester.

[0028] Adhesion can also be measured by measuring the force required to lift a metal finger adhered to the TCO material using a stylus that moves across the surface of the TCO material towards the finger. Using this measurement technique, in some embodiments the force required to lift the metal finger is at least 1 N for fingers having a width of at least 30 μm and a height of at least 8 μm.

[0029] According to a second aspect, the present invention provides a method for plating a metallic material onto a TCO material in a semiconductor device including a pn junction, the method comprising: exposing a surface of the TCO material to an electrolyte suitable for electrochemically reducing the TCO material when a current is induced through a region of the TCO material; Inducing a current flow in the TCO material by biasing the pn junction; allowing the surface of the TCO material to be reduced by an electric current and an electrolyte in a manner that improves adhesion of the metallic material to the exposed surface; plating a metal material onto the surface of the TCO material; Includes.

[0030] The TCO material can include indium tin oxide (ITO), and some of the SnO2 of the ITO can be reduced to SnO during the process, and some of the SnO can be reduced to Sn during the process.

[0031] In some embodiments, the semiconductor device is a silicon solar cell, and the method of the first or second aspect is used to form metal electrodes that allow light-generated charge carriers to be removed from the device as electrical current.

[0032] According to a third aspect, the present invention provides a manufacturing apparatus comprising a vessel suitable for containing an electrolyte and electrical equipment suitable for carrying out a method according to any one of the preceding claims.

[0033] According to a fourth aspect, the present invention provides a method for producing a medicament for the treatment of a pulmonary arthritis, comprising: A pn junction and at least one ITO layer; at least one metal contact deposited on said ITO layer; Equipped with A photovoltaic cell is provided, wherein the ITO layer has a thickness comprised between 50 nm and 100 nm and has been treated by the method of the first aspect to improve adhesion of metal contacts to the ITO layer.

[0034] In some embodiments, the ITO layer comprises In2O3 and SnO2, and the concentration of SnO2 in the ITO layer is comprised between 5% and 20%.

[0035] An advantage of embodiments of the present invention relates to a pretreatment process performed on the TCO prior to plating. This process can be performed on a TCO layer deposited on either the n-type or p-type region of a heterojunction solar cell. Advantageously, this pretreatment process is driven by a current circulating through the solar cell. This can be a current generated by light or a current induced by applying a bias voltage to the solar cell. This approach allows the "pretreatment current" to be controlled with a high degree of uniformity.

[0036] Embodiments of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which: [Brief explanation of the drawings]

[0037] [Figure 1] FIG. 1 is a flow diagram that generally illustrates steps for treating a surface portion of a TCO material in accordance with some embodiments. [Figure 2] FIG. 2 is a schematic diagram of an apparatus used to carry out the method of FIG. 1. [Figure 3] FIG. 1 is a flow diagram that schematically illustrates a process for plating a metal material onto a TCO material according to some embodiments. [Figure 4] 1 is a schematic diagram of a solar cell including a TCO layer processed according to some embodiments. [Figure 5] 1 shows an image of the metal finger after adhesion testing. [Figure 6] SEM images of the surface of a solar cell before (a) and after (b) treatment are shown. [Figure 7] 1 shows two views of the surface chemistry of the ITO layer after treatment. DETAILED DESCRIPTION OF THE INVENTION

[0038] Embodiments of the present invention relate to methods and apparatus for treating TCO materials in semiconductor devices to improve adhesion of some metals to the TCO material. Some embodiments also relate to methods for plating metals onto TCO materials that have been treated to improve metal adhesion. Some embodiments relate to photovoltaic devices that include a TCO layer, such as heterojunction solar cells, where the TCO layer has been treated to improve metal adhesion.

[0039] The TCO process takes advantage of the properties of the structure that are designed to facilitate unidirectional current flow in the semiconductor device.

[0040] Unlike other TCO treatment methods that require direct mechanical contact with the TCO material, in the methods and apparatus disclosed herein, the surface of the TCO being treated is exclusively contacted by the electrolyte. Furthermore, there is no need for induced current to flow laterally through the surface layer being treated. Instead, the induced current is directed across the surface being treated, thus enabling uniform deposition characteristics.

[0041] Referring now to Figure 1, a flow diagram 100 is shown that generally illustrates steps for treating a surface portion of a TCO material according to some embodiments. In step 105, a semiconductor device is provided that includes a structure configured to facilitate unidirectional current flow. In the case of a solar cell, the structure may include an absorber layer disposed between an electron selective film and a hole selective film. Alternatively, the structure may include a pn junction, such as in a heterojunction or homojunction solar cell.

[0042] In step 110, a surface portion of the TCO material is exposed to an electrolyte suitable for electrochemically reducing the TCO material when a current is conducted through a region of the TCO material.

[0043] In step 115, a current is induced in the semiconductor device. The current can be induced by applying a bias voltage to the semiconductor device or by exposing the semiconductor device to radiation. In some cases, the bias voltage and radiation are applied simultaneously.

[0044] When the semiconductor device is a solar cell, the TCO can be disposed as a continuous layer on either the n-type or p-type region of the solar cell. When the method is used to treat the TCO on the n-type region, a current can be induced by exposing the solar cell to electromagnetic radiation. In some cases, the light-generated current can be sufficient to perform the treatment of the TCO. In other cases, the current is promoted by applying a bias voltage to the solar cell to compensate for the self-bias of the p-n junction caused by the radiation.

[0045] When the present method is used to process the TCO on the p-type region, a forward bias voltage is required to induce current flow in the solar cell.

[0046] One advantage of this method is that the induced current flows across the layer, resulting in uniform reduction of the exposed portions of the TCO, and therefore improved deposition uniformity. Specifically, the current flows through an electrical circuit that includes the electrolyte, the solar cell, and the TCO material. This is explained in more detail in the next section with reference to Figure 2.

[0047] The current flowing through the electrolyte, solar cell, and TCO material allows for the reduction of the TCO material and improved adhesion of some metallic materials, such as copper, to the surface portions of the TCO exposed to the reducing electrolyte, compared to the adhesion of the same metal to the same TCO when the TCO is not treated by the process described above.

[0048] Referring now to Figure 2, there is shown a schematic diagram of an apparatus 200 used to carry out the method of Figure 1. The apparatus 200 comprises a chemical bath 202 suitable for containing an electrolyte solution 204. A portion of a TCO layer 207 of a solar cell 205 is exposed to the electrolyte solution 204. The solar cell 205 can be held in place using a support (not shown) or a vacuum holder (not shown) within the chemical bath. Alternatively, the solar cell 205 can be floated on the surface of the electrolyte solution 204.

[0049] Additionally, the apparatus 200 includes a wet electrode 206 submerged in the electrolyte solution and a power source 208 for applying a voltage between the wet electrode 206 and an electrode element 210 in electrical contact with the solar cell 205. The apparatus 200 includes a radiation source 212 configured to expose the solar cell 205 to radiation. The TCO layer 207 is exposed to the electrolyte solution, while the remainder of the solar cell 205 is kept dry while the method is performed.

[0050] In the embodiment of FIG. 2, the radiation source 212 is placed at the bottom of the chemical bath 202 and the photons 213 travel towards the bottom surface of the solar cell 205 .

[0051] In another embodiment, a semi-transparent electrode can be used to contact the top surface of the device and the radiation source 212 can be placed above the solar cell 205 .

[0052] A light-generated current flows through a circuit including the electrolyte 204, the solar cell 205, the TCO layer 207, the electrode 210, and the wetted electrode 206. The current flows across the TCO layer 207, providing better uniformity of the metal adhesion properties of the TCO across the layer.

[0053] A patterned mask 215 is used to select specific areas of the TCO layer 205 for processing. The mask 215 can be formed using, for example, a photoresist material. Metal can be plated through the mask 215, or the mask 215 can be removed before the plating step.

[0054] During the process, portions of the TCO layer may be etched. The concentration of metal elements in the treated portions 214 increases during the process. For example, in the case of an ITO layer, some of the SnO in the layer is first reduced to SnO and, if the process is carried out for a sufficient time, to Sn. The increased concentration of the metal element, which in the case of ITO is tin, promotes the adhesion of other metal materials, such as copper, to the TCO layer.

[0055] The electrolyte 204 contains H2SO4 at a weight concentration of 1% and Na2SO4 at a weight concentration of 0.14%. The chemical composition of the electrolyte 204 can be varied to affect the final adhesion properties of the TCO layer 207.

[0056] The surface adhesion and structural properties of the treated region 207 are related to the amount of charge transferred to the TCO material. For plating copper onto ITO, 22 mC / cm 2 It has been found that a total charge of 1 mC / cm 2 results in good adhesion properties. However, depending on the nature of the TCO and the material being plated, a total charge of 1 mC / cm 2 may be required. 2 ~50mC / cm 2 Any charge falling between these can be used.

[0057] The structural and / or electrical properties of the treated region 214 can also be controlled by varying the intensity of the light 213 and / or the magnitude of the voltage 208, thereby modulating the magnitude of the current flowing through the circuit.

[0058] Referring now to Figure 3, a flow diagram 300 is shown that generally illustrates a process for treating a TCO layer and plating a metal material onto the treated TCO layer. In steps 105, 110, and 115, the TCO material is treated as described above with reference to Figure 1. In 305, sufficient time is allowed for the TCO to be reduced. In step 310, metal is plated onto the treated surface by field-induced plating, light-induced plating, or electroplating.

[0059] Referring now to Figure 4, a heterojunction solar cell device 400 fabricated using the method of Figure 3 is shown. The solar cell 400 is formed using an n-type crystalline silicon substrate 402 disposed between two hydrogenated intrinsic amorphous silicon layers 404. The device 400 has a p-type hydrogenated amorphous silicon layer 406 on one side and an n-type hydrogenated amorphous silicon layer 408 on the other side. ITO layers 410 and 412 are disposed on the p-type and n-type hydrogenated amorphous silicon layers 406 and 408. The ITO layers have thicknesses comprised between 50 nm and 100 nm and are treated to improve metal adhesion according to the method of Figure 1.

[0060] In addition to its contact function, the ITO layer also serves as an anti-reflective coating (ARC). Control of the current used during the processing step is important because the ITO layer is etched during processing. Applicants have found that a small current allows for better control of the ITO properties during processing. A device for regulating the small current, such as a current-limiting diode (CLD), can be used in the processing equipment. Copper fingers 414 are formed on the solar cell 400 using field-induced plating, light-induced plating, or electroplating.

[0061] The adhesion of metal fingers to TCO materials can be measured using several methods, such as busbar pull tests or tape tests. Currently, there is no established industry standard for measuring adhesion.

[0062] Applicants have devised a novel method for measuring the adhesion of metal fingers to an ITO layer, which involves moving a stylus across the surface of the ITO until it encounters the sidewall of the metal finger and then pushing the finger sideways until it lifts off.

[0063] The adhesion of the fingers 414 is improved compared to copper fingers plated on a bare ITO layer. Using stylus measurements, the force required to lift a 30 μm wide metal finger with a height of 8 μm from a bare ITO layer is less than 0.2 N. In contrast, the force measured using the method of FIG. 3 is at least 1 N.

[0064] Referring now to Figure 5(a), a microscope image of the finger after adhesion testing is shown. Rather than detaching, the finger was cut from the surface. Figure 5(b) is an FIB cross-sectional image of a copper-plated finger having a width of approximately 25 μm and a height of approximately 10 μm.

[0065] Referring now to FIG. 6, there are shown SEM images of a surface before (FIG. 6a) and after (FIG. 6b) treatment with methods according to some embodiments.

[0066] Referring now to Figure 7, two diagrams of the chemical surface state of an ITO layer processed according to some embodiments are shown. Figure 7(a) shows the atomic percentages of SnO2, SnO, and Sn on the surface of an ITO layer processed according to embodiments for various charge density levels. As the charge density of the process increases, the Sn 4+ On the other hand, when the charge is increased, the proportion of SnO2 decreases. 2+ An increase in (SnO) was observed, reaching 29 mC / cm 2 When the charge density is used, the Sn element is shown in small concentration.

[0067] FIG. 7(b) confirms the results of FIG. 7(a) by showing that the concentration of metal-oxygen compounds decreases with increasing charge density of the treatment.

[0068] Any discussion of documents, acts, materials, devices, articles or the like which has been included in this specification is not an admission that any or all of such matters existed before the priority date of each claim in this application and therefore form part of the prior art base or were common general knowledge in the art to which this invention pertains.

[0069] Throughout this specification, the word "comprising" or variations such as "including" or "comprising" will be understood to mean the inclusion of the element, thing, or step or group of elements, things, or steps specified therein, but not the exclusion of any other element, thing, or step or group of elements, things, or steps.

Claims

1. 1. A method for treating a portion of a surface of a TCO layer in a semiconductor device comprising a pn junction, comprising: electrically interconnecting an electrode element to the semiconductor device and electrically interconnecting the electrode element to a wetting electrode disposed in contact with an electrolyte, wherein an induced current can flow through an electrical circuit including the electrolyte, the TCO layer, the semiconductor device, the electrode element, and the wetting electrode; exposing the portion of the surface of the TCO layer to the electrolyte, the exposed surface portion including a plurality of finger regions on which finger electrodes are formed, the electrolyte being suitable for electrochemically reducing the exposed surface portion of the TCO layer when a current is induced through the region of the TCO layer; inducing a current flow in the TCO layer by inducing a current flow in the semiconductor material of the semiconductor device by applying a voltage that forward biases the pn junction; It contains the method being carried out in a manner such that the induced current reduces a portion of the exposed surface of the TCO layer and improves adhesion of a metallic material to the exposed surface portion relative to adhesion of the metallic material to an unexposed surface portion; a portion of the exposed surface of the TCO layer is exclusively contacted by the electrolyte, the induced current is directed across the portion of the exposed surface of the TCO layer, and the induced current is uniform across the portion of the exposed surface that includes the finger region.

2. 10. The method of claim 1, wherein the TCO layer is disposed as a continuous layer over a p-type region of the semiconductor device, and the induced current flows in a direction transverse to the layer.

3. 3. The method of claim 1, further comprising controlling structural or electrical properties of the surface of the TCO layer by modulating the magnitude of the applied voltage.

4. 1. A method for treating a portion of a surface of a TCO layer in a semiconductor device comprising a pn junction, comprising: electrically interconnecting an electrode element to the semiconductor device and electrically interconnecting the electrode element to a wetting electrode disposed in contact with an electrolyte, wherein an induced current can flow through an electrical circuit including the electrolyte, the TCO layer, the semiconductor device, the electrode element, and the wetting electrode; exposing the portion of the surface of the TCO layer to the electrolyte, the exposed surface portion including a plurality of finger regions on which finger electrodes are formed, the electrolyte being suitable for electrochemically reducing the exposed surface portion of the TCO layer when a current is induced through the region of the TCO layer; inducing a current in the TCO layer by exposing the pn junction to electromagnetic radiation and inducing a current in the semiconductor material of the semiconductor device by applying a voltage between the semiconductor device and the wetted electrode in the electrolyte to reduce a voltage drop at the pn junction caused by the electromagnetic radiation; It contains the method being carried out in a manner such that the induced current reduces a portion of the exposed surface of the TCO layer and improves adhesion of a metallic material to the exposed surface portion relative to adhesion of the metallic material to an unexposed surface portion; a portion of the exposed surface of the TCO layer is exclusively contacted by the electrolyte, the induced current is directed across the portion of the exposed surface of the TCO layer, and the induced current is uniform across the portion of the exposed surface that includes the finger region.

5. 5. The method of claim 4, wherein the TCO layer is disposed as a continuous layer over an n-type region of the semiconductor device, and the induced current flows transversely to the layer.

6. 6. The method of claim 4 or 5, further comprising controlling structural or electrical properties of the surface of the TCO layer by modulating the magnitude of the induced current.

7. The method of claim 6 , wherein the magnitude of the induced current is modulated by modulating the intensity of the electromagnetic radiation.

8. The method according to any one of claims 4 to 7, wherein the electrode elements are at least semi-transparent to the electromagnetic radiation.

9. The method according to any one of claims 1 to 8, wherein the TCO layer is etched during the method.

10. The method according to any one of claims 1 to 9, carried out in such a way that the concentration of metal elements in the TCO layer at the surface increases during the method.

11. The method according to any one of claims 1 to 10, carried out in such a way that the exposed portion has an increased roughness after carrying out the method.

12. forming a mask on the TCO layer to define a patterned surface of the TCO layer that will be exposed to the electrolyte prior to exposing the surface of the TCO layer to the electrolyte. The method of any one of claims 1 to 11, further comprising:

13. The electrolyte is H ２ SO ４ The method according to any one of claims 1 to 12, comprising:

14. H in the electrolyte ２ SO ４ The method of claim 13, wherein the weight concentration of is between 0.1% and 10%.

15. The electrolyte is H ２ SO ４ and Na ２ SO ４ The method according to any one of claims 1 to 12, comprising:

16. H in the electrolyte ２ SO ４ The weight concentration of Na in the electrolyte is between 0.1% and 10%. ２ SO ４ 16. The method of claim 15, wherein the weight concentration of is between 0.05% and 0.25%.

17. The total amount of charge transferred to the TCO layer during the method is 1 mC / cm ２ ~50mC / cm ２ The method according to any one of claims 1 to 16, which is comprised between

18. The total amount of charge transferred to the TCO layer during the method is 15 mC / cm ２ ~25mC / cm ２ The method according to any one of claims 1 to 17, which is comprised between

19. The method of any one of claims 1 to 18, further comprising plating a metal onto the surface of the TCO layer.

20. 20. The method of claim 19, wherein the exposing, guiding, and plating steps are performed in a manner such that adhesion of the metal to the TCO layer is stronger than adhesion of the metal to a TCO layer that has not been treated by the method.

21. 21. The method of claim 19 or 20, wherein the adhesion of the metal to the TCO layer is stronger than 0.5 N per mm of busbar width as measured by a busbar tensile tester.

22. 22. The method of any one of claims 19 to 21, wherein the force required to lift the metal fingers attached to the TCO layer using a stylus moving along the surface of the TCO layer towards and across the fingers is at least 1 N for fingers having a width of at least 30 μm and a height of at least 8 μm.

23. The method according to claim 22, wherein the force is comprised between 1N and 3N.

24. 1. A method for plating a metallic material onto a TCO layer in a semiconductor device, the semiconductor device including a pn junction in a semiconductor material of the semiconductor device; exposing a portion of a surface of the TCO layer to an electrolyte suitable for electrochemically reducing the TCO layer when a current is induced through a region of the TCO layer, the exposed portion of the surface including a plurality of finger regions in which finger electrodes are formed; inducing a current in the TCO layer by inducing a current in the semiconductor material, the current in the semiconductor material being induced by applying a voltage that forward biases the pn junction; allowing the current and the electrolyte to reduce a portion of the exposed surface of the TCO layer in a manner that improves adhesion of the metallic material to a portion of the exposed surface including the finger regions; plating the metallic material onto a portion of the exposed surface of the TCO layer; Including, A method in which a portion of the exposed surface of the TCO layer is exclusively contacted by an electrolyte, the induced current is directed across the portion of the exposed surface of the TCO layer, and the induced current is uniform across the portion of the exposed surface that includes the finger region.

25. 1. A method for plating a metallic material onto a TCO layer in a semiconductor device, the semiconductor device including a pn junction in a semiconductor material of the semiconductor device; exposing a portion of a surface of the TCO layer to an electrolyte suitable for electrochemically reducing the TCO layer when a current is induced through a region of the TCO layer, the exposed portion of the surface including a plurality of finger regions in which finger electrodes are formed; inducing a current in the TCO layer by exposing the pn junction to electromagnetic radiation and inducing a current in the semiconductor material by applying a voltage between the semiconductor device and a wetted electrode in the electrolyte to reduce a voltage drop at the pn junction caused by the electromagnetic radiation; allowing the current and the electrolyte to reduce a portion of the exposed surface of the TCO layer in a manner that improves adhesion of the metallic material to a portion of the exposed surface including the finger regions; plating the metallic material onto a portion of the exposed surface of the TCO layer; Including, A method in which a portion of the exposed surface of the TCO layer is exclusively contacted by an electrolyte, the induced current is directed across the portion of the exposed surface of the TCO layer, and the induced current is uniform across the portion of the exposed surface that includes the finger region.

26. The TCO layer comprises indium tin oxide, SnO ２ A method according to any one of claims 1 to 25, wherein a portion of is reduced to SnO during the method.

27. The method of any one of claims 1 to 26, wherein the TCO layer comprises indium tin oxide, and part of the SnO is further reduced to Sn during the method.

28. The method of any one of claims 1 to 27, wherein the semiconductor device is a silicon solar cell.

29. A manufacturing apparatus comprising a vessel suitable for containing an electrolyte and electrical equipment suitable for carrying out the method according to any one of claims 1 to 28.

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